Checking Your Car’s Tire Pressure: Why It’s So Important

Stephen Fogel
February 26, 2019


Your tires are where the rubber meets the road — literally — so it’s important to make sure they’re in top shape. This includes making sure they have the right amount of air pressure inside them.

Maintaining the correct tire air pressure gives your car better fuel economy, more responsive steering and longer tire life. Tires can lose 1 pound per square inch (PSI) of pressure each month, even in the best conditions. Low air pressure will lead to rapid heat buildup inside the tire, which can cause blowouts. That’s why you need to check your tires regularly, and add air when needed.

First, you need a tire gauge

To check your tires, you’ll need a tire pressure gauge. You can either use the gauge attached to the air compressor at the gas station or you can use your own gauge.

The tire gauges at gas stations are free, even if the air machine usually isn’t. But these gauges are notoriously inaccurate. They get dropped on the ground and sometimes are run over by cars. A better option is carrying your own gauge. 

The most cost-effective type to buy is a digital electronic tire gauge, which gives you precise numerical pressure readings, usually down to the nearest half-pound of pressure. They’re inexpensive and long-lasting, although you will occasionally need to replace the battery.


Next, pick the right time 

Tire pressure is directly affected by temperature. Tires get warm when you drive, and warm tires will produce a higher pressure reading than when they are cool. The manufacturer’s recommended pressures apply to cool tires, so the best time to check the pressure is after your car has been parked for at least three hours. Overnight is even better.

Your tire pressure is also affected by the outside air temperature. Tires that are properly inflated for cold winter conditions will show higher pressures in the summertime. Similarly, tires that have the correct pressures during the heat of the summer will read low when winter arrives. Seasonal adjustments are necessary, even when you’re checking them regularly.

Find the recommended tire pressures

Most car have their recommended tire pressures printed on a sticker on the driver’s door jamb. If you don’t see it there, check your owner’s manual. There will usually be separate pressures listed for the front and the rear tires. 

Write down the pressures on a piece of paper if you think it will make it easier to remember them. The recommended pressures may be listed in more than one type of measuring unit, such as PSI, KPA, BAR or kg/cm2. PSI is the most common unit in the U.S. Whichever unit of measurement you use, be sure that your pressure gauge has been set to read out in the same units.

tire inflation

Find a source of air

To inflate your tires, you will need access to a source of compressed air. Your best options are the air compressor at your local gas station or getting your own portable compressor.

To use the air compressor at your local gas station, you’ll need to park near the machine and bring enough quarters to get it running. Make sure to remove all your tire valve caps first, before you insert the quarters. 

Being able to check and fill your tires, at home or anywhere else, with your own portable compressor comes with many advantages. It’s more convenient, your tires won’t get heated up from driving to the gas station (which can throw off the readings), and it can be used in an emergency.

Look for a reasonably priced, compact air compressors that you can keep in your vehicle. Many have 12-volt plugs that can be powered directly by your car. This is an excellent investment, one that will be paid back quickly by not having to feed quarters into an air machine.

How to add or release air

  1. If you don’t have your own air compressor, drive to the nearest gas station or convenience store and park where the hose will reach all of your tires. If you’re using your own portable air compressor, park your vehicle in a location that is safe from passing traffic.
  2. Remove all of your car’s tire valve caps, placing them in your pocket or inside the car so that they don’t get lost.
  3. Check each of your tires with your gauge first, pressing the gauge firmly against the tire valve.
  4. If the gauge readings are lower than the manufacturer’s recommended pressures, you ‘ll need to add air to those tires. Start up your air compressor and add air to each tire that needs it. 
  5. If any of the gauge readings are higher than the manufacturer’s recommended pressures, you will need to release air from those tires by pushing the gauge against the valve gently.
  6. Recheck each tire with your gauge, adding or releasing air until you get the correct reading for each tire. Screw the tire caps back on tightly.

» MORE: When to get new tires, and tips for buying them

Other tire tips

How often should you check your tire pressure?

A good rule of thumb is to check your tire pressures once a month. But if there’s been a sudden change in how your car feels, rides, handles or stops, it’s always a good idea to check your tires. A puncture or a slow leak can happen at any time. 

What about my spare tire?

You should also check your spare tire at regular intervals, so it will be properly inflated in case you get a flat. Check your owner’s manual or the spare tire itself for its correct inflation pressure. 

What if I need to put air in my tires when they are hot?

If you need to add air to a low tire that’s warm from driving, you can add 3 or 4 PSI to the recommended pressure for that tire in order to compensate for the effects of the heated air. Once that the tire has cooled, check it again and adjust it to the correct pressure reading. 

What does the “Maximum Pressure” number on the tire mean?

The “Maximum Pressure” number molded into the tire sidewall is the highest pressure the tire can safely hold. It’s usually a much higher number than what the manufacturer recommends, and should not be used as tire pressure guidance. 

Should I put nitrogen in my tires, instead of air?

Some tire and car dealers are keen on selling you a service that replaces the air in your tires with nitrogen. They claim many benefits, but they usually neglect to tell you one important fact: Air is already made up of 78% nitrogen!

So they’re really only replacing the 22% of the air that’s not already nitrogen. Putting pure nitrogen in your tires has little or no benefit for the average car. 

What about cars with TPMS?

All vehicles sold in the U.S. after Sept. 1, 2007, have a tire pressure monitoring system (TPMS) that monitors the air pressure in the tires, and alerts the driver when the pressure drops to a dangerous level.

But that doesn’t mean you can get lazy. Most TPMS systems won’t alert you until one or more of your tires have lost 25% of their recommended pressure. While the TPMS warning may prevent a blowout, a pressure loss of 25% is more than enough to negatively affect your fuel economy, tire wear and the way your car handles. So keep checking those tires.

Stephen Fogel

About the Author

Stephen has been an automotive enthusiast since childhood, owning some of his vehicles for as long as 40 years, and has raced open-wheel formula cars. He follows and writes about the global automotive industry, with an eye on the latest vehicle technologies.

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